The human body has biometric information that identifies an individual. Some types of biometric information are used for identifying and authenticating an individual. For example, it is known that biometric information that may be used for authentication includes fingerprints, retina, iris, face, blood vessels, deoxyribonucleic acid (DNA), and the like.
With the recent developments in biometric authentication technologies, various types of individual authentication apparatuses have become available. These apparatuses recognize the features of a living body, that is, a part of the human body, so as to authenticate an individual. For example, palm vein authentication technology is used in transactions in bank accounts, door security systems, log-in authentication in personal computers, and the like. In biometric authentication, biometric information acquired upon authentication is verified against biometric information acquired upon registration (registered template).
In order to improve the accuracy of authentication using biometric information, it is preferable to acquire biometric information of a certain level of accuracy each time authentication is performed. However, acquired biometric information is not always the same, and there is a change every time acquisition is performed. Therefore, verification of biometric information involves calculating a verification score that indicates the similarity between a registered template and the acquired biometric information, and comparing the calculated verification score with a determination value. There has been proposed a verification apparatus capable of, even if there is a change in the acquired biometric information, performing verification with high accuracy by correcting a verification score (see, for example, Japanese Laid-open Patent Publication No. 2008-40874).
However, since the amount of features contained in acquired biometric information varies between individuals, and the difficulty of authentication varies from user to user, regardless of the scheme of authentication. Further, for example, the amount of features that may be acquired from the biometric information also varies with the surrounding environment in which the biometric information is acquired, such as temperature, humidity, outside light, the position of the sensor, individual differences between sensors, and the like.
Accordingly, authenticating a specific user (who inherently has only a small amount of feature information, or who is not familiar with authentication) may be more difficult than authenticating other users. Similarly, authenticating a user in a specific environment may be more difficult than in other environments.
One of the issues in authentication technology is to reduce the difficulty in authenticating a user under such specific conditions so as to increase the authentication rate and thus to improve the usability.